An image forming apparatus that prints (forms) an image taken by an image-taking apparatus, such as a digital still camera, on printing paper usually has a function that performs index printing. In index printing, all images recorded on a recording medium or all images stored in a specified folder are reduced and printed on one or more sheets of printing paper by a predetermined number or batch (for example 20 images per printing paper). A user can take a glance over the images recorded on the recording medium or stored in the folder by executing this process of printing on the printing papers. Furthermore, with a conventional image forming apparatus, the user can print a plurality of images that the user freely selects on one or more sheets of printing paper by a predetermined number or batch (hereafter referred to as “multiple image printing”). In multiple image printing, 2, 4, 9, or 16 images are reduced and printed on one sheet of printing paper, for example.
Thus, in index printing and multiple image printing, a plurality of images are printed on one sheet of printing paper, but if the image data of one image is corrupted, then the image cannot be printed on the sheet of printing paper. In this case, various measures are conceivable such as eliminating blanks between the images, but in some image forming apparatuses, index printing or multiple image printing is performed by leaving those regions blank in which images corresponding to corrupted image data are to be arranged (see JP 64-51778A, for example). The empty portions on the printing paper after the printing let the user know that corrupted image data is included in the series of image data that is subjected to index printing or multiple image printing, or in other words, that the process of printing is not performed properly.
However, if the above-described process is performed in index printing or multiple image printing and all image data of the plurality of images to be printed on one sheet of printing paper is corrupted (if all 20 sets of image data associated with 20 images to be printed on one sheet of printing paper are corrupted in index printing, for example), then a printing paper on which no reduced images is printed is output from the image forming apparatus and the printing paper is wasted. Such a situation arises when even though all or some of the image data recorded on the recording medium is subjected to image processing, the image data after the image processing is corrupted by malfunctioning of the image processing, for example.
In view of the above-described problems, it is an object of the present invention to provide an image forming apparatus that does not output a printing paper on which not a single image is printed, if a plurality of images is to be printed on a printing paper, as in index printing or multiple image printing or the like.